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Theses

Dynamique des anneaux et des satellites planétaires : application aux arcs de Neptune et au système Prométhée-Pandore

Abstract : First, this thesis considers the dynamics of co-orbital satellites. The problem of the Lagrangian points is extended to derive general results on the existence of stationary configurations. For N co-orbital satelllites with small but otherwise arbitrary masses, the existence of equilibrium points depends on the parity of N. If N is odd, then for any arbitrary angular separation between the satellites, there always exists a set of masses which achieves stationarity. Physically acceptable solutions (positive masses) restrict this existence to sub-domains of angular separations. If N is even, additional conditions must be verified. The case N = 3 is treated completely, giving all the possible solutions and their stability. For N > 3, numerical methods are given. These results are applied to explain the confinement of Neptune's ring arcs, with a model compatible with the latest observations (Dumas et al., 1999; Sicardy et al., 1999b; de Pater et al., 2004) : the arcs are trapped between small co-orbital satellites (with radii r < ~5 km), which are in a stable stationary configuration. The system is numerically stable under the effects of the perturbations due to the satellite Galatea. The origin and the evolution of such a system are discussed. Then the dynamics of Prometheus and Pandora is studied. Recent HST observations (French et al., 2003) show anticorrelated sudden changes in the mean motions, which arise from chaotic interactions between the two satellites (Goldreich et Rappaport, 2003a). Chaos is due to the overlap of four 121 :118 apse-type mean motion resonances (Goldreich et Rappaport, 2003b). Taking into account the perturbations by the major saturnian satellites, the chaotic motions are numerically confirmed. By fitting the numerical integrations to the HST data, Prometheus and Pandora's masses are derived. They are equivalent to mean densities of about 0.5 g/cm3. The fits allow to produce an ephemeris of the two satellites during the Cassini tour. Finally, performing long term integrations, a transfer of angular momentum from Prometheus and Pandora to the co-orbital satellites Janus and Epimetheus is detected, which could increase the lifetime of the Prometheus-Pandora system.
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https://tel.archives-ouvertes.fr/tel-00008103
Contributor : Stéfan Renner <>
Submitted on : Monday, January 17, 2005 - 4:42:20 PM
Last modification on : Monday, December 14, 2020 - 9:45:51 AM
Long-term archiving on: : Friday, April 2, 2010 - 8:55:46 PM

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  • HAL Id : tel-00008103, version 1

Citation

Stéfan Renner. Dynamique des anneaux et des satellites planétaires : application aux arcs de Neptune et au système Prométhée-Pandore. Astrophysique [astro-ph]. Observatoire de Paris, 2004. Français. ⟨tel-00008103⟩

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